The present invention relates to a rolling bearing arranged to be connected to other machine components to journal the same during rotation and comprising a number of rolling bodies arranged to roll in an annular raceway around a centre of rotation for the bearing, an outer main element in the form of a ring or tube outside said annular raceway with a rolling surface for the rolling bodies that faces substantially inwards towards the centre of rotation in said annular raceway, and an inner main element with a rolling surface for the rolling bodies that faces substantially outwards away from the centre of rotation in said annular raceway.
Rolling bearings of the type specified above for journalling machine components for rotary motion are categorized with respect to the design of the rolling bodies into ball bearings, roller bearings and needle bearings. The two first-mentioned types, in particular, are found in many different sizes and designs for more or less heavy loads and for different sorts of load. Examples include grooved ball bearings, angular contact ball bearings and self-aligning bearings.
One category of bearings on the market is bearings of a standard design, xe2x80x9ccatalogue productsxe2x80x9d, which have a cylindrical outer envelope and a cylindrical shaft hole. The utility of such bearings is in essence limited to their function as bearings; and the machine parts to be journalled to each other must be adapted by machining before connection to the outer envelope or shaft hole, respectively, of the bearing.
Another category of rolling bearings is bearings that, in addition to their utility as bearings, are adapted to be connected to a specific machine part. A typical example is bearings for front wheels for bicycles. In such a bearing, one part is in the form of a hub spindle, inside the ends of which raceways are arranged for the rolling bodies, which are balls, of the bearing. The opposite inner raceways are designed as discs with a threaded hole, which is designed so that the two discs can be threaded on a mounting axle for the wheel with the hub spindle therebetween. The hub spindle is provided with external flanges with holes for fastening the spokes of the wheel. Such a bearing is thus designed as a complete hub assembly, adapted to be attached with the axle in the fork for the wheel and forming a mounting unit for the spokes. Products within this category are in the following denoted as xe2x80x9cdesignated bearingsxe2x80x9d. These are most commonly made as bulk products and can be widely used within a certain product group.
Finally, mention is made of a category that can be termed xe2x80x9cintegrated bearingsxe2x80x9d. The bearing is there integrated into a larger construction complex, in which the machine components are designed for other functions besides a bearing function. An example that can be mentioned is hub assemblies for vehicle wheels, which are often referred to as xe2x80x9chub unitsxe2x80x9d in the motor industry. Hub assemblies are there designed for a specific vehicle model and comprise, in addition to the operative components necessary for the bearing, an outer hub component for attaching the wheel and an inner hub component with devices for wheel suspension and drive members, for instance.
In all the mentioned categories of rolling bearings, it is common that the rolling surfaces are designed as ground raceways adapted to the shape of the rolling bodies. These raceways must be finished with great precision and high-tensile steel must be used in the main elements where the raceways are fashioned. The material as well as the machining costs for such designs result in relatively high prices for rolling bearings manufactured in this way. Attempts have therefore been made to fashion the raceways in another way. A known method is to line the raceways with thin sleeves of high-tensile steel. In this way, it is not necessary to use such high-quality materials throughout the entire bearing assembly, whilst it is possible to make the quality of the materials in the thin sleeve very high by compression and choice of extremely durable materials. In the patent specification DE, A, 384914 (Thalheimer) it is suggested that such a lining is made out of a helically wound wire, which is shown to be laminating-rolled and ground to form the support for the rollers in a rolling bearing. Another suggestion is known from the patent specification DE, A, 846 646 (Franke), in which the raceways are formed by annular wire rings abutting the rolling bodies, in the form of balls. By these means, the machining of the main components of the bearing that are rotatable relative to each other is considerably reduced, from the grinding of entire raceways to the cutting of grooves in which the wire rings can be fixed. The wire rings can be made of compressed high-tensile steel as a support for the rolling bodies. In this way, it is possible to compensate, to some extent, for the reduced contact surface between main component and rolling body as compared with ground raceways.
Using the standard rolling bearing with its cylindrical outer envelope and cylindrical hole as well as ground raceways as an archetypal design for rolling bearings, one can, in elucidating what has here been stated, identify certain development trends in the known art. One of these is represented by the categories mentioned as designated bearings and integrated bearings. In these categories certain further functions, besides the pure bearing function, have been accommodated, which is not the case with standard bearings. The other development trend described herein is the evolution of methods of forming the raceways of the bearing other than grinding the rolling surfaces into the main components of the bearing. This development is the one most germane to efficiency improvement and the reduction of manufacturing costs and greater freedom of choice in materials. This development trend may be relevant to standard bearings, as well as designated bearings and integrated bearing assemblies.
The purpose of the invention is to provide a design for the main elements of the bearing, such that it can be manufactured, even in small runs, in an efficient and cost-effective way, and which provides plentiful opportunities for the design of designated roller bearings and integrated bearings with additional functions besides the pure bearing function. In this way, assemblies comprising bearings for rotary motion can be manufactured at a lower cost than is possible using standard rolling bearings for the bearing function. The invention is primarily intended to be utilized in connection with assemblies for light-duty service.
In the device in accordance with the invention, one or both of the main elements of the bearing is formed by winding a helical spring in such a way as to form the raceway of the rolling bodies, but the spring is also fashioned to form parts with a function other than the bearing function by extending the spring by further turns of winding in one or both axial directions from the part of the spring forming the raceway. In this way, additional functions, such as the connection to further raceways in rolling bearings with several rows, the fashioning of connection and attachment elements for fastening to the journalled machine structure, or the elastic suspension of the journalled unit can be accommodated at an insignificant extra cost over and above the cost of the winding for the raceway.